1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device and a method for manufacturing the nitride semiconductor light emitting device.
2. Description of Related Art
A conventional method for manufacturing the nitride semiconductor laser device will be described with reference to FIGS. 10 and 11. FIG. 10 is a schematic drawing showing inside of a conventional nitride semiconductor laser device, and FIG. 11 is a drawing showing an external view of the conventional nitride semiconductor laser device.
In the conventional method for manufacturing the nitride semiconductor laser device, a nitride semiconductor laser chip 403 is soldered to a sub mount 402 as a heatsink with solder 406, and then the sub mount 402 with the soldered nitride semiconductor laser chip 403 is soldered onto a holding substrate (stem) 401 with solder (not shown). Then, a pin 405 provided to the holding substrate (stem) 401 is connected electrically to the nitride semiconductor laser chip 403 with a wire 404. Next, a work box is prepared, which is filled up with air having dew point controlled to be under −20 degrees centigrade by eliminating moisture (hereinafter referred to as dry air), for example. As shown in FIG. 11, the nitride semiconductor laser chip is sealed together with the dry air in the work box by using a cap 407 with a glass lens 407a that passes a laser beam. Thus, the nitride semiconductor laser device is manufactured. The nitride semiconductor laser device manufactured by the above-mentioned process is operated in the dry air.
In general, if the nitride semiconductor laser device is operated in dry air, it can work stably more than 3,000 hours. However, even if it is sealed in dry air, the seal may be insufficient, for example. In this case, the dry air may leak slightly so that atmospheric air (that contains moisture and is not controlled about its dew point) may enter inside the cap. If the atmospheric air enters inside the cap described above, there is observed a phenomenon that voltage increases rapidly after 100 to 1000 hours or so. In some elements the voltage increases more than 1 volt, and others may cause further deterioration resulting in stop of oscillation.
The same phenomenon as the case where the dry air leaks so that the atmospheric air enter inside the cap is observed in the case where the nitride semiconductor laser chip 403, which is not sealed by the cap 407 in dry air, is operated in the atmospheric air that contains moisture and is not controlled about its dew point (hereinafter referred to as an open air package). Such a phenomenon is unique to a nitride semiconductor laser device, which is not observed in case of a GaAs system laser element that has been put to practical use conventionally. Described above, there is a problem that voltage may increase resulting in a malfunction if the dry air leaks so that the atmospheric air enter inside the cap due to an excessive stress while the nitride semiconductor laser device is assembled or operated.